Well-known member

You can make custom language files.. but the user has to select that language.
There are no functions currently present in XenForo that are similar to the language ones of WBB in which the users can select a language and then only see posts that are made in that language.
In fact, WBB is one of the few scripts that I am aware of that do that (paid)... and I currently run XenForo, IPS and WBB.